> I presume that you meant "Setup" -> "Build Methods" as the place to enter the search paths?
Correct, under tab INCLUDE directories and LIB directories for the CLANG build. I do not have anything in the include / libs directories for GCC build method.
> But what struck me as odd is that while the CLANG build method has clang++ as the compiler, the GCC build method has no entry for the compiler - ummm???
Same for me, however it seems to work. I can select the GCC build for the AddressBook example and it builds and runs.
> Now I'm not sure if U++ under POSIX systems is using gcc, g++ or clang++. Or perhaps its using more than one, depending on what it's compiling?
I believe it uses GCC or CLANG depending on what you pick. I always choose CLANG (from the toolbar).
> The ide package is failing to build on my system as is
I had no issues building the IDE package (#16739). I have the files "/usr/include/c++/11/bits" and "/usr/include/c++/9/bits".